Field of the Invention
The present invention relates to a defect detection apparatus and method. More particularly, the present invention relates to an apparatus and method for detecting a defect of an image having a periodic pattern.
Discussion of the Related Art
FIGS. 1 and 2 are diagrams showing a related art method of detecting a defect of an image having a periodic pattern.
As illustrated in FIG. 1, the related art method shifts an image for detecting a defect, measures an error of an image before and after the shift, and extracts a pattern period by using a shifting value of when the error is minimized.
For example, when px denotes a value shifted in a perpendicular direction and py denotes a value shifted in a horizontal direction, the related art method progressively increases px and py and shifts an image through repetition for extracting a repetition period of a pattern, analyzes image errors before and after the shift to calculate an image having the minimum error. That is, px and py of when an error between images is the minimum are extracted as a pattern period.
However, in the related art, since an image should be repeatedly shifted until the minimum error is measured for extracting a pattern period, a considerable calculation time is expended.
Moreover, when the related art method of detecting a defect of an image having a periodic pattern is applied to an image having a complicated shaped pattern as illustrated in FIG. 2, it is inaccurate to measure an error of an image having such a complicated pattern. For this reason, it is difficult to extract a sufficiently accurate pattern period.